Abstract A015: A novel diagnostics approach to Ductal Carcinoma In Situ (DCIS) with potential impact on the therapeutic algorithms

Background: Ductal carcinoma in situ (DCIS) of the breast is a heterogeneous group with variable clinical presentation. 70-80% of DCIS are classified as grade 3 (Van Nuys Classification). They are treated according to grade and extension of the lesion, as was the standard treatment for invasive breast cancer in the 1970`s. Molecular genetic studies of invasive breast carcinomas (BC) have defined a molecular subclassification. In routine diagnostics, we use surrogate markers like estrogen receptors (ER), progesterone receptors (PR), and human epidermal growth factor receptor 2 (HER2) as tools to stratify for treatment. The individual results of these surrogate markers have resulted in a complex treatment algorithm. In contrast, still all DCIS grade 3 are given the same treatment. Aim: To investigate the molecular subtypes of DCIS diagnosed at the Department of Pathology, Akershus University Hospital (Norway). Materials: 483 histological specimens of DCIS at Akershus University Hospital, Dep. of Pathology, during 1996-2018. All relevant background information was recorded. Methods: All histological sections have been reassessed, and the grading has been confirmed independently by two experienced pathologists. An eventual peritumoral inflammatory component was made note of. All grade 3 DCIS with representative paraffin blocks were submitted for immunohistochemistry (IHC). The investigated markers were ER, PR, Ki-67 and HER-2. Results: The age ranged from 33-90, with a mean and median of 57 years. 10.4% were grade 1, 3.9% as grade 2 and 85.7% as grade 3. The size of DCIS ranged from 0,5 to150 mm, with mean 28 mm and median of 20 mm. 64 patients had an invasive component, 51 of them with a size of <5 mm (pT1a), and 13 > 5 mm but < 10 mm (pT1b). 33 (6,8%) patients were diagnosed with a recurrent DCIS or cancer (minimum 1year after primary DCIS diagnosis). Six patients were deceased (1 was diagnosed with new ipsilateral DCIS 3 years later, 2 with cancer in the contralateral breast, 2 with cancer in ipsilateral breast and 1 with new DCIS in the ipsilateral breast). The preliminary results of immunohistochemical studies of 245 cases indicate: Luminal A: 30.7% (Ki-67 <14%), Luminal B: 42% (Ki-67> 14%) and non-luminal 27.3%. Around 33% of the non-luminal cases are expected to be triple negative. Histomorphologically, we have found peritumoral lymphoid cells in 31% of cases, and all of these (100%) are DCIS grade 3. Conclusions: The molecular subtypes identified in invasive breast carcinomas are all represented in DCIS G3 and further studies might reveal the possibility of a more adapted treatment algorithm, as in invasive BC. The peritumoral inflammatory cell infiltrates will be investigated in future studies.

Citation Format: Hossein Schandiz, Daehoon Park, Yan Liu Kaiser, Marianne Lyngra, Ingrid Solvang Talleraas, Jürgen Geisler, Torill Sauer. A novel diagnostics approach to Ductal Carcinoma In Situ (DCIS) with potential impact on the therapeutic algorithms [abstract]. In: Proceedings of the AACR Special Conference on Rethinking DCIS: An Opportunity for Prevention?; 2022 Sep 8-11; Philadelphia, PA. Philadelphia (PA): AACR; Can Prev Res 2022;15(12 Suppl_1): Abstract nr A015.